voltage drop

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enireh

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Canyon Lake,TX
a customer had her slab done for the barn and stubbed 1 1/2 pvc out. the barn is 300' from the service so we are running 4/0 copper for a 150 amp feed to the barn. I thinking about having a pvc junction box at the barn and come out of it with 2/0 copper so we can get in the 1 1/2 pvc to the panel inside. not orthodox I know
 
4/0 copper would be fine for 150 amps at 300 feet. It is about a 4% drop on 240V so you still have 230 amps and general the power company delivers more than 240. I am sure the actual load is not 150 amps
 
enireh said:
a customer had her slab done for the barn and stubbed 1 1/2 pvc out. the barn is 300' from the service so we are running 4/0 copper for a 150 amp feed to the barn. I thinking about having a pvc junction box at the barn and come out of it with 2/0 copper so we can get in the 1 1/2 pvc to the panel inside. not orthodox I know
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I hope you're not going to try running the 4/0 in that 1-1/2" conduit!
 
enireh said:
a customer had her slab done for the barn and stubbed 1 1/2 pvc out. the barn is 300' from the service so we are running 4/0 copper for a 150 amp feed to the barn. I thinking about having a pvc junction box at the barn and come out of it with 2/0 copper so we can get in the 1 1/2 pvc to the panel inside. not orthodox I know
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A 150A feeder does not equal 150A worth of load. My whole house doesn't draw 50A on an average day and won't break 80A if I fire up everything in it.

I agree with infinity, use 2/0 for the whole run.

If you insist on 4/0 there is nothing wrong with changing over to 2/0 at the end of the run.
 
Good luck putting 2- 2/0 copper, a neutral of some size and an equipment grounding conductor in 1-1/2" pvc. It may fit but I question whether or not it meets code.
 
According to my calculator you would need 350 kcmil aluminum to get below 3% at 150 amps.
 
So the consensus at the moment would be 350kcm Al for the long run for voltage drop, transitioning in a junction box (maybe also the building disconnect?) to whatever copper will carry the load allowed by the breaker for the run through the 1 1/2" pipe to a panel inside?
 
GoldDigger said:
So the consensus at the moment would be 350kcm Al for the long run for voltage drop, transitioning in a junction box (maybe also the building disconnect?) to whatever copper will carry the load allowed by the breaker for the run through the 1 1/2" pipe to a panel inside?
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Ummmmm, no. We have no idea what the voltage drop is since there is no mention of the load. I'm gonna bet it's under 150A, I'll even be so bold as to take the under at 100A.
 
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